Electronic elements such as organic EL (Electro Luminescence) elements, organic photoelectric transducer elements and organic transistors have an organic layer as one of components. Such an electronic element is easily degraded when coming into contact with the air in comparison with an electronic element not having an organic layer. Therefore, in an electric device in which electronic elements having an organic layer is mounted, sealing is performed in order to prevent degradation of the elements.
The sealing is performed, for example, by arranging a sealing member so as to surround electronic elements mounted on a support substrate and by bonding a sealing substrate to the support substrate with the sealing member interposed therebetween. That is, a region surrounded by the support substrate, the sealing substrate, and the sealing member is insulated from the outside. A member that hardly allows gas to pass through is used as the sealing member. Frit seal using glass as such a sealing member is contemplated as one of sealing methods. Frit is flake-like or powder-like glass (hereinafter also simply referred to as “frit glass powder”) that melts at low temperatures as compared with normal glass. A paste-like fit agent in which fit glass powder is dispersed in a solvent is used for fit seal.
In fit seal, first, a frit agent is supplied to a support substrate having electronic elements mounted thereon so as to surround the electronic elements, and then, preliminary baking is generally performed in order to remove a solvent component in the fit agent. Thereafter, a sealing substrate is bonded to the support substrate with the frit agent interposed therebetween. Then, the frit agent is irradiated with laser light so that the fit agent is heated and fused. When the irradiation of laser light is stopped, the temperature of the fit agent drops and the fit agent is hardened again. The sealing member is thus formed, and the region surrounded by the support substrate, the sealing substrate, and the sealing member is hermetically sealed.
The heating of the fit agent is performed by irradiating throughout the entire periphery thereof with laser light. However, when heating variations occur at that time, the fused state varies from place to place. As a result, the adhesion between the sealing substrate or the support substrate and the sealing member, or the characteristics of the sealing member becomes uneven, leading to reduction in reliability of the sealing. Therefore, in frit seal, it is necessary to heat and fuse the fit agent uniformly throughout the entire periphery.
However, irradiating throughout the entire periphery of the fit agent with laser light alone usually causes heating variations in the frit agent. The frit agent is provided on a prescribed underlying layer. In general, the underlying layer is not always formed of a uniform member. In the underlying layer, an easily heated part and a hardly heated part exist. Therefore, even if the frit agent is irradiated with laser light uniformly, heating variations may occur in the frit agent due to the thermal characteristics of the underlying layer. For example, in an electric device, a lot of electric wirings for inputting/outputting electrical signals to electronic elements are provided so as to intersect the fit agent. The heating characteristics differ between a place where the electric wiring is provided and a place where the electric wiring is not provided when irradiated with laser light. For example, in a case where laser light having a spot diameter larger than the width of the fit agent is used, or in a case where part of laser light passes through the frit agent, the underlying layer is also irradiated with the laser light, so that the temperature of the underlying layer as well as the frit agent is increased. The electric wiring is heated by laser light more easily than any other member. Therefore, transfer of heat from the frit agent provided on the electric wiring to the underlying layer is suppressed. As a result, the temperature of the frit agent provided on the electric wiring becomes higher than the frit agent provided in the place where electric wiring is not provided. As described above, irradiating the frit agent uniformly with laser light alone does not allow the fit agent to be uniformly heated and fused.
Then, in a conventional technique, a plurality of holes are provided in a stripe-shaped electric wiring in a region where the stripe-shape electric wiring and the fit agent intersect each other, whereby a temperature increase of the electric wiring is prevented during heating, and the fit agent is heated and fused uniformly throughout the entire periphery thereof (see, for example, Patent Literature 1).